Startled westside neighbors then watched a 29-year-old man run out of his house and drive off. He was suffering from life-threatening burns while driving, Clark said.

When police officers arrived, no one was home except for two dogs with singed fur. They found more than a dozen butane canisters and a large quantity of marijuana in the bathroom, and the bathroom's doors were completely blown off.

Dominican Hospital Emergency Room employees called police and alerted them that a badly burned man had just arrived with his girlfriend. He was flown in a helicopter to a Bay Area trauma center in critical condition.

Over on the 700 block of Third Street, three young men were cooking hash oil on Sept. 29 when several explosions blasted out of their apartment and a fire ignited. When Santa Cruz police officers and firefighters arrived, even more explosions happened as butane canisters continued to burst.

"In spite of the additional explosions, firefighters were able to contain the blaze and minimize damage to the surrounding structures," Clark said.

The trio nearly died and suffered severe third-degree burns that melted away flesh, police said. They fled the apartment building and were rushed to an emergency burn center. As of Wednesday afternoon, they were still listed in "extremely critical condition" by hospital staff.

"The investigation revealed that the three individuals were involved in hash oil production at the time of the blast," Clark said.

The process to make hash oil is extremely dangerous. It's made by using flammable chemicals with extremely combustible butane to extract concentrated THC from marijuana plants. The end product is thick and yellow, so it's commonly referred to as "honey oil."

In February, FEMA issued an alert to police and fire departments warning of an increase seen in hash oil production explosions on the West Coast from Seattle, Wash. down to California.